Surface comparison microscope having light conducting members providing grazing and diffuse illumination



May 17, 1949. N. LINDGREN ET AL 2,470,176

SURFACE COMPARISON MICROSCOPE HAVING LIGHT CONDUCTING MEMBERS PROVIDING GRAZING AND DIFFUSE ILLUMINATION Filed March 18, 1946 3 Sheets-Sheet l FIG.2.

NILS LINDGREN PAUL A. ROOS Snnentors (Ittorneg May 17, 1949. N. LINDGREN ET AL 7 SURFACE COMPARISON MICROSCOPE HAVING LIGHT CONDUCTING MEMBERS PROVIDING GRAZING AND DIFFUSE ILLUMINATION Filed March 18, 1946 3 Sheets-Sheet 2 NILS LINDGREN PAUL A. ROOS 3nventors 2,470,176 LIGHT NG May 17, 1949. N. LINDGREN ET AL SURFACE COMPARISON MICROSCOPE HAVING RS PROVID E ILLUMIN ING GRAZI ATION 3 Sheets-Sheet 3 CONDUCTING MEMBE AND DIFFUS Filed March 18, 1946 I NILS- LINDGREN PAUL A. ROOS Enventors (Ittorneg Patented May 17, 1949 SURFACE COMPARISON MICROSCOPE HAV- ING LIGHT CONDUCTING MEMBERS PRO- VIDING GRAZING AND DIFFUSE NATION ILLUMI- Nils Lindgren, Irondequoit, and Paul A. Boos,

Greece, N. Y., assignors to Banach 8r Lomb ptical Company, Rochester, N. Y., a corporation of New York Application March 18, 1946, Serial No. 855,094

4 Claims. 1

The present invention relates to a surface comparison microscope of the type in which the images of standard and specimen surfaces are adjacently formed in a single field.

It is an object of the present invention to provide a. novel surface comparison microscope of the above type which is light and easy to handle while being compact and sturdy.

It is a further object to provide a device in which the surfaces under comparison are equally illuminated by a single light source.

It is another object .to provide such a device wherein principal illuminating beams of sub- -stantially parallel light rays fall upon the surfaces under comparison at grazing incidence and wherein diffused light rays additionally illuminate the surfaces in the proximity of said beams.

A still further object is to provide such-a device in which the illuminating light rays are conducted through transparent, refractive light conducting members for transmission of both the principal and the auxiliary diffused light rays.

It is a further object to provide such a device with interchangeable and removable holders which are adapted to retain either a single or a plurality of standard surfaces in viewing position.

It is another object to provide such a device in which the light conductors are composed of multiple sections and the standard surface holder receives one of such sections fixedly in a position to direct and intensify the beam in close proximity to the standard surface.

Further objects and advantages will be apparent to those skilled in the art by reference to the following description and accompanying drawings in which:

Fig. 1 is a side elevation partly in section of a preferred embodiment of the invention,

Fig. 2 is a longitudinal section of the holder for a plurality of standard surfaces,

Fig. 3 is a cross section taken on line 3-3 of Fig. 2,

Fig. 4 is 'a diagrammatic side elevation of the optical parts,

Fig. 5 is an end elevation of the optical parts shown in Fig. 4,

Fig. 6 shows the view in the eyepiece,

Fig. 7 is a fragmentary side elevation partly in section of the casing and illuminating means,

Fig. 8 is a perspective view of the invention assembled on a stand,

Fig. 9 is a longitudinal section of a modification of the invention for holding a single standard surface, and

Fig. 10 is a sectional view taken along the axis of a chuck member for holding the standard surfaces. I

In Fig. 1 of the drawings, a body member or casing generally indicated at III having the angular extensions Ii and I2 is provided throughout the length of each extension with coplanar passages I3 and I4 which terminate inwardly in an open chamber IS. The outer ends of passages I3 and I4 terminate infaces l6 and I1 respectively which are normal to the axes thereof.

Means fo'r holding a plurality of blocks l8 having different standard or master surfaces I3 thereon in viewing position across the outer end of passage I3 is provided in the form of a rotatable disk on which clamping chucks 2| are secured by any suitable means such as screws 22 and washers 22'. The body 23 of the clamping chuck is positioned on the disk 20 by the shank 24 which closely but releasably fits into holes 25 in the disk. Means for arranging the surface markings of the standard surface is in a predetermined manner with relation to an illuminating beam therefor and in an optical field is provided in the form of a cross slot 26, as shown in Fig. 10, in which an instrument blademay be inserted to rotate the chuck 2| after block I8 has been chucked therein. A clamping ring 21 threaded to the chuck 2| by threads 28 is provided with a tapered lip 29 which overhangs the edge of the standard surface l9 to retain it in a fixed position. The lip 29 insures that the stand; ard surface is is held accurately normal to the axis of the optical system regardless of the lack of uniformity in thickness or parallelism of the front and back surfaces of the master block, the variation being taken care of by a clearance space 30. The block 18 rests against a pressure plate 30' and is pressed against the clamping ring 21 to bring the surface l9 into an established object plane by a compression spring 3| seated in th body 23 of the chuck. It will be seen, as shown in Fig. 3, that the surface markings on the master surfaces ii! are all oriented in a standard manner in the clamping chucks 2! for advantageous reasons which appear later in this description.

Rotatable disk 20 is journaled upon a spindle 32 projecting from a stationary casing 33 and is held thereon by a cap screw 34. A cylindrical extension 35 on disk 20, having a corrugated .peripheral surface 36, enables the operator to index the disk 2|! to align any selected master surface is across the passage l3 and the rotatable disk is retained in this position by a spring detent 31 beyond the rear of casing 33 to act as a mount-- ing stud 88 for attaching the rotary member 20 and casing 83 to the body ear 38, the members 20 and 33 being held thereon by thumb nut 48. Casing a is also provided with an opening 4i in axial alignment with the body passage It so that any master surface I! may be aligned therewith. A dowel pin 42. fixed in the casing a and slidably received in an opening 43 of body extension ll, further assists in aligning the passag II with opening 4|,

Means for locating and holding aspecimen surface 44 in correct viewing position at the outer end of the body passage I4 is provided in the form of a cylindrical slidable locator 45 yieldably mounted by suitable means such as springs 46 and 41 on the end of body extension l2. Locator 48 is prevented from rotating by a pair of slidable rods 48 and 49 closely fitting the bores 50 and II in body extension l2, said rods being fixed to the integral interior cars 52 and 53 on locator 48 which fit freely within slots 54 and 55 cut across the end of body extension ii. The ears l8 and II are prevented from moving out of slots 54 and 58 by a fixed retainer plate 56 mounted across the slots against face I! within the locator 45 and having an inwardly bevelled port I! therethrough in alignment with the objective lens 8|. Means for arranging the surface markings of circular or angular specimen surfaces 44 with reference to the surface markings of the standard surface l8 are provided in the form of recesses of any suitable shape such as the V II which are formed transversely across the outer rim 88 of the locator 45. The outer surface of the plate 86 is located in the object plane of lens I so that the specimen surface may be located properly by placing it against plate 58.

Optical means for forming enlarged images of the master or standard surface l9 and the specimen surface 44 is provided. in the form of objective lenses 80 and 8| adjustably mounted by means of threads 62 and 63 in passages l3 and I4 in the body extensions I I and I2, respectively, and having the object planes thereof coincident with the master and specimen surfaces. The images formed by the objective lenses 60 and ii are united along a dividing line 64 in a single field ll, Fig. 6, by a compound prism 68 which is fixed within chamber l and has the portion 81 of its interface below the intersection of the optical axes coated with an opaque layer to refiect half of the rays transmitted by the objective lens 80 while obstructing half of therays transmitted by the objective lens iii in the wellknown manner. Means for viewing the composite field I thus formed by the objective lenses is afforded by placing a collective lens 68 and an ocular 89 on the optical axis of the objective 6|.

According to the present invention, means are provided for substantially equally illuminating the standard and specimen surfaces at grazing incidence comprising a single light source such as the electric lamp I8 centrally mounted in a cylindrical chamber II which is equidistant from both the master and specimen surfaces l9 and 44, and a plurality of light conductors I2 and 13 in axial alignment with the filament I4 of lamp Ill.

The light conductors l2 and 13, formed of glass or other transparent material such as acrylic resins, are aligned to cooperate, respectively, with the outer light-conducting members 11 and Il which are formed of a similar-transparent, li htconducting material. The ends of the conductou I2 and II which are adjacent the lamp II are preferably formed with integral hyperboioidal lens surfaces 18 and 88, respectively, so that light rays from the lamp III will be transmitted in a substantially parallel beam, indicated at I, axially of the members I2 and 13 and into the members TI and I8. The ends of the members II and IO, which are respectively adjacent the surfaces II and 44, are formed with the polished angularly disposed surfaces 82, 83 and 82, 83' so as to direct the beams of parallel rays 8i onto the respective surfaces l8 and 44 at grazing incidence.

In addition to directing beams of collimated rays onto the surfaces at grazing incidence, the light conducting members also function to direct scattered or diffused light rays 88 onto the surfaces l8 and 44 at random angles so as to illuminate the valleys or depressions of the surfaces and thereby enable the observer to determine more accurately the depths of the valleys or depressions. While the collimated parallel beams 8| are directed substantially parallel to the axes of the conducting members, the scattered or diffused light rays are directed along the conducting members by internal reflection on the side walls thereof as indicated at 86. The conducting member 11 is fixedly mounted in a bore in casing 33 so that when the latter is secured to the body extension II, the member 11 will be held in operative relation to the member 12.

In Fig. 9 of the drawings, a modification oi the invention is illustrated in which a single block 88 having a standard surface 88 thereon is firmly held in the object plane of the objective lens and against the body face It by a separable adapter clamp 89. The clamp has a base II which fits against the body face l6 and is removably attached thereto by any suitable means such as the stud 92 traversing the body ear II and the thumb screw 93. Light conducting member I1 is fixed in the base Si in an angular position similar to the position of member 11 in the casing 33 of the disk type holder 28 so as to refiect the light beam 8! onto the master surface I8 at grazing incidence through a port 94 into a light chamber 95. Chamber 98 is closed at one side by a locating plate 96 having a flared opening 91 in axial alignment with objective lens 80, the outer surface of the plate, being in the object plane of the lens 80 so as to correctly position the standard surface block 88. Proper alignment of the objective lens 68 and flared opening 91 is secured by setting a dowel pin 98 solidly in the base 9| so as to slidably enter the hole 43 in the body extension II. A spring finger l8l pivoted at I02 on the post I03 and having an inclinable pressure pad I04 thereon, presses the master block 88 firmly against the working surface of plate 96.

In order to improve the portability and handling of the instrument in use, a convenient handle IDS is added to the body It. The instrument may also be detachably secured to a stand I06 by suitable clamping means indicated generally at III.

In use, the surface comparison microscope may be held manually in contact with the specimen surface 44 or may be mounted on the stand I in which case the specimen surface 44 is brought into contact with the locator 45. In either case stantially surface markings appear to erectly meet the dividing line 54 in the field 65. The light is turned on and the specimen surface 44 is pressed against the locator 45. When a specimen surface 44 of round or angular cross section is examined, the surface markings are properly aligned in the field 65 by placing the specimen in the recess 58. If the specimen under comparison is fiat or substantially so, the specimen surface is brought into focus of the lens 6| by pressing it against the plate 56 and turning the specimen until the surface markings, appearing in the field 55, are aligned in a colinear manner. The observer may then examine the surfaces under comparison and manipulate either of the surfaces to aid in judging the surface finish.

Although but certain forms of the invention have been shown and described in detail, it will be understood that other forms are possible and changes may be made in the form and arrangement of the parts without-departing from the spirit of the invention as defined in the appended claims.

We claim:

1. In a surface comparison microscope, a body member having passages extending therethrough and a chamber connecting said passages, a locating member for holding a specimen surface in juxtaposition to one of said passages, a separable adapterv member for holding a standard surface ment therewith for directing from said source a beam of substantially parallel light rays at grazing incidence upon said surfaces and additionally providing from said source an illumination of diffused light rays on the surfaces.

2. A surface comparison microscope comprising a body having two hollow extensions angularly disposed to each other, means for holdinga specimen surface against the open end of one extension and a part detachably secured to the v body for holding a standard surface against the Open end of the other extension, means within a the body and extensions for forming in a field adjacent images of the respective surfaces, and means for equally illuminating said surfaces comprising a single light source mounted within a recess in the body and a pair of aligned subcylindrical transparent members mounted within a bore intersecting said recess and in optical alignment. with sai source and specimen surface, a second pair of substantially cylindrical transparent members in optical alignment with said source and standard surface, the member of the second pair which is adjacent the source being mounted in a bore in the body, the other member of the second pair being mounted within said part adjacent the standard surface.

3. In a microscope having means for holding a'surface and means for forming an image of the surface, the combination of means for illuminating the surface by directing substantially parallel light rays onto the surface at grazing incidence and additionally illuminating the surface by diffused light rays, said last named means comprising a light source having a filament, lens means positioned adjacent the source with the focal point of the lens means located at the filament, and transparent rod means extending from the lens means to a point adjacent the surface, the axes of the lens means and rod means being substantially coincident, the rod means having an angular reflecting face adjacent the surface at such an angle as to provide grazing incidence of light rays on the surface whereby light rays from one point on the filament will be colllmated by the lens means and transmitted through the rod means while light rays from other points on the filament will be directed onto the side walls of the rod means and successively reflected thereby to provide additional diffuse illumination on the surfaces;

4. A surface comparison microscope comprising a body having two hollow extensions disposed at substantially right angles to each other, means for respectively holding specimen and standard surfaces against the open ends of the extension, means within the body and extensions for forming in a field adjacent images of the two surfaces, and means having substantially identical optical paths for equally illuminating said surfaces comprising a single light source mounted within a recess in the body and two substantially similar pairs of aligned cylindrical transparent members mounted within bores in the bodyin alignment with the source, the ends of the members adjacent the source being formed with lens surfaces, the ends of the members adjacent the surfaces having angular reflecting faces whereby light rays from the source are directed in colllmated beams through the members and thence reflected by the reflecting faces at grazing incidence onto the surfaces while other light rays from the i source are internally reflected by the walls of the members and pass through the members to dilfusely illuminate the surfaces.

.NILS LINDGRENi PAUL A. ROOS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Minton et al. June 12, 1942 

